﻿using System;
using System.Collections.Generic;
using System.IO;
using System.Security.Cryptography;
using System.Text;
using System.Windows.Forms;

namespace ShipinJiami
{

    /// <summary>
    /// 异常处理类
    /// </summary>
    public class CryptoHelpException : ApplicationException
    {
        public CryptoHelpException(string msg) : base(msg) { }
    }
    /// <summary>
    /// CryptHelp
    /// </summary>
    public class Common
    {
        private const ulong FC_TAG = 0xFC010203040506CF;

        private const int BUFFER_SIZE = 128 * 1024;

        /// <summary>
        /// 检验两个Byte数组是否相同
        /// </summary>
        /// <param name="b1">Byte数组</param>
        /// <param name="b2">Byte数组</param>
        /// <returns>true－相等</returns>
        private static bool CheckByteArrays(byte[] b1, byte[] b2)
        {
            if (b1.Length == b2.Length)
            {
                for (int i = 0; i < b1.Length; ++i)
                {
                    if (b1[i] != b2[i])
                        return false;
                }
                return true;
            }
            return false;
        }

        /// <summary>
        /// 创建DebugLZQ ,http://www.cnblogs.com/DebugLZQ
        /// </summary>
        /// <param name="password">密码</param>
        /// <param name="salt"></param>
        /// <returns>加密对象</returns>
        private static SymmetricAlgorithm CreateRijndael(string password, byte[] salt)
        {
            PasswordDeriveBytes pdb = new PasswordDeriveBytes(password, salt, "SHA256", 1000);

            SymmetricAlgorithm sma = Rijndael.Create();
            sma.KeySize = 256;
            sma.Key = pdb.GetBytes(32);
            sma.Padding = PaddingMode.PKCS7;
            return sma;
        }

        /// <summary>
        /// 加密文件随机数生成
        /// </summary>
        private static RandomNumberGenerator rand = new RNGCryptoServiceProvider();

        /// <summary>
        /// 生成指定长度的随机Byte数组
        /// </summary>
        /// <param name="count">Byte数组长度</param>
        /// <returns>随机Byte数组</returns>
        private static byte[] GenerateRandomBytes(int count)
        {
            byte[] bytes = new byte[count];
            rand.GetBytes(bytes);
            return bytes;
        }

        /// <summary>
        /// 加密文件
        /// </summary>
        /// <param name="inFile">待加密文件</param>
        /// <param name="outFile">加密后输入文件</param>
        /// <param name="password">加密密码</param>
        public static void EncryptFile(string inFile, string outPath, string password)
        {
            try
            {
                String md5 = GetMD5HashFromFile(inFile).ToUpper();
                String outFile = Path.Combine(outPath, md5 + ".LDATA");
                if (File.Exists(outFile))
                {
                    return;
                }
                String fileName = Path.GetFileName(inFile);
                byte[] byts = Encoding.UTF8.GetBytes(fileName);
                byte[] blen = System.BitConverter.GetBytes(byts.Length);
                int toplen = byts.Length + blen.Length + 1;
                byte[] tops = new byte[toplen];
                tops[0] = (byte)blen.Length;
                Array.Copy(blen, 0, tops, 1, blen.Length);
                Array.Copy(byts, 0, tops, blen.Length + 1, byts.Length);
                using (FileStream fin = File.OpenRead(inFile),fout = File.OpenWrite(outFile))
                {
                    long lSize = fin.Length; // 输入文件长度
                    int size = (int)lSize;
                    byte[] bytes = new byte[BUFFER_SIZE]; // 缓存
                    int read = -1; // 输入文件读取数量
                    int value = 0;
                    // 获取IV和salt
                    byte[] IV = GenerateRandomBytes(16);
                    byte[] salt = GenerateRandomBytes(16);
                    // 创建加密对象
                    SymmetricAlgorithm sma = Common.CreateRijndael(password, salt);
                    sma.IV = IV;
                    // 在输出文件开始部分写入文件信息
                    fout.Write(tops, 0, tops.Length);
                    // 在输出文件开始部分写入IV和salt
                    fout.Write(IV, 0, IV.Length);
                    fout.Write(salt, 0, salt.Length);
                    // 创建散列加密
                    HashAlgorithm hasher = SHA256.Create();
                    using (CryptoStream cout = new CryptoStream(fout, sma.CreateEncryptor(), CryptoStreamMode.Write),
                        chash = new CryptoStream(Stream.Null, hasher, CryptoStreamMode.Write))
                    {
                        BinaryWriter bw = new BinaryWriter(cout);
                        bw.Write(lSize);

                        bw.Write(FC_TAG);

                        // 读写字节块到加密流缓冲区
                        while ((read = fin.Read(bytes, 0, bytes.Length)) != 0)
                        {
                            cout.Write(bytes, 0, read);
                            chash.Write(bytes, 0, read);
                            value += read;
                        }
                        // 关闭加密流
                        chash.Flush();
                        chash.Close();

                        // 读取散列
                        byte[] hash = hasher.Hash;

                        // 输入文件写入散列
                        cout.Write(hash, 0, hash.Length);

                        // 关闭文件流
                        cout.Flush();
                        cout.Close();
                    }
                }
            }
            catch (Exception Err)
            {
                Console.WriteLine("加密异常:" + Err.Message);
            }
        }

        /// <summary>
        /// 解密文件
        /// </summary>
        /// <param name="inFile">待解密文件</param>
        /// <param name="outFile">解密后输出文件</param>
        /// <param name="password">解密密码</param>
        public static void DecryptFile(string inFile, string outPath, string password)
        {
            try
            {
                int outValue = 0;
                long lSize = -1;
                byte[] oldHash = null;
                byte[] curHash = null;
                int read = -1;
                // 创建打开文件流
                using (FileStream fin = File.OpenRead(inFile))
                {
                    int size = (int)fin.Length;
                    byte[] bytes = new byte[BUFFER_SIZE];
                    int value = 0;
                    int len = fin.ReadByte();
                    byte[] tem1 = new byte[len];
                    fin.Read(tem1, 0, tem1.Length);
                    int len2 = System.BitConverter.ToInt32(tem1, 0);
                    byte[] tem2 = new byte[len2];
                    fin.Read(tem2, 0, tem2.Length);
                    String filename = Encoding.UTF8.GetString(tem2);
                    String outFile = Path.Combine(outPath, filename);
                    byte[] IV = new byte[16];
                    fin.Read(IV, 0, 16);
                    byte[] salt = new byte[16];
                    fin.Read(salt, 0, 16);
                    SymmetricAlgorithm sma = Common.CreateRijndael(password, salt);
                    sma.IV = IV;
                    value = 32;
                    // 创建散列对象, 校验文件
                    HashAlgorithm hasher = SHA256.Create();
                    using (FileStream fout = File.OpenWrite(outFile))
                    {
                        using (CryptoStream cin = new CryptoStream(fin, sma.CreateDecryptor(), CryptoStreamMode.Read),
                            chash = new CryptoStream(Stream.Null, hasher, CryptoStreamMode.Write))
                        {
                            // 读取文件长度
                            BinaryReader br = new BinaryReader(cin);
                            lSize = br.ReadInt64();
                            ulong tag = br.ReadUInt64();
                            if (FC_TAG != tag)
                                throw new CryptoHelpException("文件被破坏");
                            long numReads = lSize / BUFFER_SIZE;
                            long slack = (long)lSize % BUFFER_SIZE;
                            for (int i = 0; i < numReads; ++i)
                            {
                                read = cin.Read(bytes, 0, bytes.Length);
                                fout.Write(bytes, 0, read);
                                chash.Write(bytes, 0, read);
                                value += read;
                                outValue += read;
                            }
                            if (slack > 0)
                            {
                                read = cin.Read(bytes, 0, (int)slack);
                                fout.Write(bytes, 0, read);
                                chash.Write(bytes, 0, read);
                                value += read;
                                outValue += read;
                            }
                            chash.Flush();
                            chash.Close();
                            fout.Flush();
                            fout.Close();
                            curHash = hasher.Hash;
                            // 获取比较和旧的散列对象
                            oldHash = new byte[hasher.HashSize / 8];
                            read = cin.Read(oldHash, 0, oldHash.Length);
                        }
                    }
                }
                if (outValue != lSize)
                {
                    throw new CryptoHelpException("文件大小不匹配");
                }
                if ((oldHash.Length != read) || (!CheckByteArrays(oldHash, curHash)))
                {
                    throw new CryptoHelpException("文件被破坏");
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message); 
            }
        }
        /// <summary>  
        /// 获取文件的MD5码  
        /// </summary>  
        /// <param name="fileName">传入的文件名（含路径及后缀名）</param>  
        /// <returns></returns>  
        public static string GetMD5HashFromFile(string fileName)
        {
            try
            {
                FileStream file = new FileStream(fileName, System.IO.FileMode.Open);
                MD5 md5 = new MD5CryptoServiceProvider();
                byte[] retVal = md5.ComputeHash(file);
                file.Close();
                StringBuilder sb = new StringBuilder();
                for (int i = 0; i < retVal.Length; i++)
                {
                    sb.Append(retVal[i].ToString("x2"));
                }
                return sb.ToString();
            }
            catch (Exception ex)
            {
                throw new Exception("GetMD5HashFromFile() fail,error:" + ex.Message);
            }
        }
    }
}
